Transgenic avidin maize is resistant to storage insect pests

Avidin is a glycoprotein found in chicken egg white, that sequesters the vitamin biotin. Here we show that when present in maize at levels of ≥100 p.p.m., avidin is toxic to and prevents development of insects that damage grains during storage. Insect toxicity is caused by a biotin deficiency, as shown by prevention of toxicity with biotin supplementation. The avidin maize is not, however, toxic to mice when administered as the sole component of their diet for 21 days. These data suggest that avidin expression in food or feed grain crops can be used as a biopesticide against a spectrum of stored-product insect pests

Alarm Pheromones and Chemical Communication in Nymphs of the Tropical Bed Bug Cimex hemipterus (Hemiptera: Cimicidae)

The recent resurge of bed bug infestations (Cimex spp.; Cimicidae) and their resistance to commonly used pesticides calls for alternative methods of control. Pheromones play an important role in environmentally sustainable methods for the management of many pest insects and may therefore be applicable for the control of bed bugs. The tropical bed bug, Cimex hemipterus, is a temporary ectoparasite on humans and causes severe discomfort. Compared to the common bed bug, Cimex lectularius, little is known about the chemical signalling and pheromone-based behaviour of the tropical species. Here, we show that the antennal morphology and volatile emission of C. hemipterus closely resembles those of C. lectularius and we test their behavioural responses to conspecific odour emissions. Two major volatiles are emitted by male, female and nymph C. hemipterus under stress, (E)-2-hexenal and (E)-2-octenal. Notably, nymph emissions show contrasting ratios of these compounds to adults and are further characterized by the addition of 4-oxo-(E)-2-hexenal and 4-oxo-(E)-2-octenal. The discovery of this nymph pheromone in C. hemipterus is potentially the cause of a repellent effect observed in the bio-tests, where nymph odours induce a significantly stronger repellent reaction in conspecifics than adult odours. Our results suggest that pheromone-based pest control methods developed for C. lectularius could be applicable to C. hemipterus, with the unique nymph blend showing promising practical properties

Bed bug deterrence

A recent study in BMC Biology has determined that the immature stage of the bed bug (the nymph) signals its reproductive status to adult males using pheromones and thus avoids the trauma associated with copulation in this species. The success of this nymphal strategy of deterrence is instructive. Against the background of increasing problems with bed bugs, this research raises the question whether pheromones might be used to control them

Chemically Mediated Arrestment of the Bed Bug, Cimex lectularius, by Volatiles Associated with Exuviae of Conspecifics

Extracts of the exuviae (cast skins) of nymphal bed bugs (Cimex lectularius) were analyzed for volatile compounds that might contribute to arrestment of adult bed bugs. Four volatile aldehydes, (E)-2-hexenal, 4-oxo-(E)-2-hexenal, (E)-2-octenal, and 4-oxo-(E)-2-octenal were consistently detected in the headspace of freshly shed exuviae regardless of the developmental stages from which the exuviae were obtained. Quantification of the aldehydes in the solvent extracts of homogenized fresh, 45- or 99-d aged 5th instar exuviae indicated that the aldehydes are present in the exuviae and dissipate over time, through evaporation or degradation. Microscopic observation of the fifth instar exuviae indicated that the dorsal abdominal glands on the exuviae maintained their pocket-like structures with gland reservoirs, within which the aldehydes might be retained. Two-choice olfactometer studies with the volatiles from exuviae or a synthetic blend mimicking the volatiles indicated that adult bed bugs tend to settle close to sources of the aldehydes. Our results imply that the presence and accumulation of bed bug exuviae and the aldehydes volatilizing from the exuviae might mediate bed bugs' interaction with their microhabitats

Whole body extract of Mediterranean fruit fly males elicits high attraction in virgin females

The search for effective female attractants emanating from the host or body of fruit flies has been an area of intensive research for over three decades. In the present study, bodies of male Mediterranean fruit flies, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), were extracted with diethyl ether or methanol and subjected to gas chromatography-mass spectrometry. Analysis revealed substantial qualitative and quantitative differences between males from a laboratory culture and wild males captured alive in an orchard. Most notably, the hydrocarbon sesquiterpene (+/-)-alpha-copaene, which is known to be involved in the sexual behaviour of the species, was found in substantial amounts in wild males, but was not detected in laboratory males. In laboratory tests, 15 laboratory or wild male equivalents of diethyl ether extracts or combined diethyl ether and methanol extracts, or, to a lesser extent, methanol extracts alone, were found to attract virgin females. In a citrus orchard, traps baited with combined diethyl ether and methanol extracts of wild males attracted significantly more virgin females than traps baited with various doses of pyranone or blends of other compounds identified in the extracts or reported in the literature, such as ethyl acetate, ethyl-(E)-3-octenoate, and 1-pyrroline. Traps baited with blends of compounds, however, displayed substantial attractiveness compared to control (non-baited) traps. These results are important for better understanding the mating system of C. capitata as well as for further improving existing monitoring and control systems

Does natal habitat preference modulate cereal kernel preferences in the rice weevil?

The influence of larval diet source in Sitophilus oryzae (L.), a primary grain feeder, on the choice of a new cereal host by young adult was investigated through a multiple choice comparative bioassay. For this purpose, virgin male and female adults, which had been reared as immatures in different grain commodities, were monitored according to their food preference in cylindrical arenas containing whole kernels of maize, rice, barley and wheat. The adults showed a clear individual preference for maize kernels, regardless of the previous food experience, sex and also the interval on which the adults are exposed to food. Males were much more mobile than females and visited more vigorously different commodities before the final choice. Female response was found to be related with male response to specific food sources. Hence, our results indicate that there was no natal habitat preference induction, since maize was, in most cases, the final commodity choice